A. Field of the Invention
The present invention relates to reflectance photometers, and, more particularly, the present invention relates to reflectance photometers in which the light of absorption is modulated by linear polarizers.
B. Description of the Background Art
Reflectance photometers commonly are used for quantitative chemical analysis, such as analysis of body fluids. A known quantity of body fluid, such as a drop of blood, is placed on a reactive reagent strip impregnated with a chemical reactive with a quantitatively unknown body fluid component, e.g. blood glucose. The fluid is wiped off the strip and the reagent strip is placed within or in contact with a readhead of a reflectance photometer where the strip is illuminated with a controlled, diffuse light and the light reflected from the strip is measured. The reaction product formed on the reagent strip will reflect a known amount of light for each different amount (concentration) of each body fluid component analyzed. The light reflected is sensed by a detector in the readhead. Thus, for each different reflection measured from the reagent strip, the quantity of the particular body fluid component in the sample analyzed is known.
Even though present generation reagent strips have reached a high degree of perfection, they still show a number of intrinsic drawbacks. For example, there is reduced resolution at higher glucose levels, and the light levels of scattered light become separated by lower and lower margins the higher the glucose level within the body fluid to be determined. This highly nonlinear response of reagent strips leads to an upper linear and of sensitivity of measurable glucose concentrations; for example, there are some reagent strips the sensitivity of which does not exhaust beyond 400 mg/dL. It is possible to modify the reagent pads chemically to overcome these drawbacks but chemical modification is difficult and expensive. It is desireable to overcome these drawbacks using an entirely new procedure not requiring chemical modification.